If you don't have a supported version of Visual Studio installed, the product will install a complete Fortran development environment based on Visual Studio 2010 Shell. (Note, however, the evaluation version doesn't do this.) So you don't have to buy Visual Studio separately in order to develop Fortran applications. If you do want to separately install Visual Studio, Intel Visual Fortran will integrate into it (currently 2008, 2010, 2012 and 2013). See Which versions of Microsoft Visual Studio are supported by various Intel compiler versions? for more details.